What does an MEP do?

Let’s start by taking a look at what exactly you are voting for, especially given the results of a recent poll that only 11% of voters could confidently name one of their MEPs. At a very basic level an MEP is your representative within the European parliament. Twelve times a year they will be expected to travel to the chamber in Strasbourg. All other parliamentary business takes place in Brussels, where there is also a chamber.

EU legislation dealt with by the parliament must also be approved by the Council of the European Union and vice versa. The council is the body made up of representatives of each member state at ministerial level, with its presidency revolving between member states every six months.

The European parliament has no say in matters of defence, education, housing, health or law and order. However, it is able to legislate on environmental matters, trade, consumer protection and employment law.

In a way it's unsurprising that people don't feel much of a connection with their MEPs. As we will discuss later on, MEPs are voted in on a party list which means you vote for the party rather than the individual person. Several of them represent broad regional territories and they also generally only spend a few days of their week in their home country doing constituency work.

How MEPs are elected

MEPs are elected through a form of proportional representation, which theoretically means that the number of parliamentarians should match the party’s overall support in the country.

However, it’s not quite that easy because the UK has 73 MEPs (one more than 2009) broken down into 12 broad electoral regions and dividing equally between those is difficult. The voting system that is used to try to rectify those issues is a variation on the famous D’Hondt method.

The best way to imagine it is like a series of first past the post elections for all the seats available with the party's vote divided by the number of seats they have plus one.

For example, in a hypothetical constituency Ukip have 50,000 votes, Labour have 39,000, the Conservatives have 26,000 and the Lib Dems 11,000. Ukip would win the first round by virtue of having the most votes. The number one name on their regional list would therefore be the first MEP.

Before the second round that 50,000 would be divided by two (Ukip's seat plus one) and as a result Labour would take the second round as their 39,000 is more than 25,000. We've animated all the voting rounds above so you can see how it would happen in real time.

What happened last time and how have things changed since?

2009 was not a good European election for Labour. Dissatisfaction with Gordon Brown's government was pretty high and that translated into a paltry showing of 15.8% across the UK and 13 MEPs (-6) compared to 27.9% for David Cameron's Conservatives and 25 MEPs (-2) respectively.

This meant that Ukip took second place with 16.6%, which at the time was a huge victory for the party even though they got the same number of seats as the Labour party.

Polling for this election shows that we're set for a much bigger win for Ukip with Joe Twyman, director of political research at YouGov, saying as early as March that Farage's party was likely to take the most votes.

Since April, the majority of polls listed on YouGov's UK Polling Report have put Ukip in first place with them hovering around 28% - that's a huge rise on their 2009 figures.

Averaging the most recent five polls, Labour come out in second place with 26.6% followed by the Tories who get 23.4%. The Greens are fourth with 8% closely followed by the Liberal Democrats with 7.4%.

Best prospects for the parties

It is very difficult to forecast any election in the UK. Nate Silver has blogged extensively about the difficulty of doing so for Westminster elections. The issues are largely down to a paucity of regional polling data and that is true here too.

The best we can do is to use what is called a uniform swing. This is essentially seeing the extent to which all the regions varied from the national vote during the last election (i.e the south-east gave 7.1 more percentage points to the Conservative party than they achieved nationally) and applying those to current polling numbers. It's flawed but much better than trying to directly convert national figures into number of seats.

Using that average of the last five polls on UK Polling Report, we come out with the following forecast:

Ukip would be the evening's winners, with their 28.2% of the vote translating into 23 seats (+11) making them the joint biggest UK party.

Labour's 26.6% would give them 8 more seats taking them to 22, which would make up for a poor showing during the last elections.

The Conservatives' healthy 25 would be cut by seven to eighteen. The BNP, as expected, would be wiped out and the SNP would take an extra seat in Scotland.

For reference sake we've also included a graphic using the projection of the EU wide PollWatch 2014, which gives more seats to Ukip and to Labour and fewer to the Tories. We've also added in what it would look like if some recent regional polling figures from ComRes, were correct - bear in mind with that poll that the base is so small for the specific regions it seems like it's produced a very optimistic swing to Ukip.

On all projections it is the Liberal Democrats who look set to take the biggest pounding. Our uniform swing sees them getting 7.4% of the national vote, which would lead to their number of MEPs shrinking from 12 to just one. What's worse for them is that their one MEP in the south east would be taken extremely narrowly. This means we're forced to ask the question...

Could the Lib Dems come fourth and get no MEPs?

Despite having better national popular polling numbers than the Green party the Lib Dems could very feasibly lose all their MEPs at this election.

In our uniform swing model, a drop of just 0.18 percentage points in the Lib Dem vote would see them lose their prospective south east MEP to Ukip. Ouch.

The strongest regions for Ukip in our model are the south-west and the West Midlands where we forecast them to get 33.8% and 33% of the vote respectively.

This highlights some of the issues with the uniform model, given that we know Ukip's regional power base is the east of England region. Under our model Nigel Farage's party will comfortably get a seat in every region except Scotland and Northern Ireland.

Labour should comfortably take most of the MEPs they do win. Their biggest risk of getting fewer would be a weak showing in the east-midlands or with a stronger than expected Lib Dem turnout in Wales. They could possibly snatch an MEP from the Conservatives in Scotland, from the Greens in London or from Ukip in the north-west.

What this all means for Europe

2009's election was very much a rebuke to Gordon Brown's Labour government and hardly anything to do with the issues that surround Europe.

With the success of Ukip, this one has much more of a focus on the EU but one that is not really about the parliament but about the wider issue of Britain's membership.

Expect the potential stories to emerge from it to be very shrouded in domestic focus - Ukip threatening the Tories, the Liberal Democrats possibly getting wiped out at the next election.

However, the choices that are being made here will not be domestic at all in their legislative impact. All the parties likely to have MEPs elected at the European parliament are part of cross-continental political blocs fighting for overall control of legislature.

Would it surprise you to know that two of the biggest parties - Conservatives and Ukips - are members of relatively small groupings within the EU?

In a post tomorrow we will look at how the UK vote could potentially impact on the wider European parliament.

Methodology

To get our projections for the national vote we averaged out the last five on the UK polling report at the time of writing (ICM/Sunday Telegraph - May 15, ComRes/Independent on Sunday - May 15, YouGov/Sun - May 14, Opinium - May 12, ICM/Guardian - May 11).

With Scotland and Wales specifically there was a lack of data from the national polls which we could use to apply a uniform swing to so we went out in search of specific polls for those region. For Scotland, we took the last five polls from What Scotland Thinks, which we used to provide specific averages (no uniform swing).

We only found one regional poll for Wales by Cardiff University in April, which was what we used to distribute the number of MEPs there.

Because Northern Ireland elects exclusively non-Westminster parties, we have allowed for that happening again and listed all of their MEPs as "Others".

This article was amended on May 20. It previously stated that there were 74 UK MEPs instead of 73 and MEPs had six sessions each year in Strasbourg when they have twelve.